Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
11'~954~
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The present invention relates to an extraction
device or apparatus for separating the liquid components
from solid components in a li~uid-solid mixture.
A known extraction device comprising a drivable
screw which is rotatable in a press barrel, a screw flight
helically disposed thereon, and radially extending pins
which extend into the press barrel in the direction of the
screw axis. The pins extend substantially to this axis
although their depth of penetration is adjustable. Gaps
are formed in the flights which correspond to the diameter
of the pins.
In United States Patent Specification ~o.
3,981,658, there is disclosed a device for extracting
liquids from solid-liquid mixtures which has pins protrud-
ing through the press barrel. Such pins extend radially to
the screw and prevent the material to be extracted from
rotating with the screw. Such pins cause an adequate
conveying pressure to be built up.
An object o the present invention is to provide
an extraction device whereby extracted liquid may be dis-
charged directly from the site at which it is extracted
without a substantial drop in pressure occurring due to
such discharge. This pressure drop occurs in known filter
presses.
According to the present invention there is pro-
vided an apparatus for separating liquid components from
solid components of a liquid-solid mixture, comprising:
a) a hollow press barrel defining a relatively
low pressure feed region and a relatively higher pressure
pin-barrel region,
b) a drivable screw rotatable in said barrel,
said screw having a longitudinal axis, a base, and a screw
flight helically disposed thereon, said screw flight being
formed with axially spaced gaps extending radially entirely
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around said base in the areas o~ said gaps,
c) a plurality of radially inwardly directed pins
passing into said pin-barrel region of said press barrel,
the radially inner ends of said pins extending substantially
to said base of said screw in the regions of said axial
gaps and forming narrow radial gaps with said screw base,
the presence of said pins in said pin-barrel region effect-
ing a substantial buildup of pressure in such region thereby
resulting in the release of liquid from said mixture t the
diameter of each said pin being less than the length of the
adjacent axial gap so as to permit rotation of said screw,
each said pin having an axially extending throughbore
including a first, open end adjacent the base of said screw
and a second end remote from said screw base, said through-
bores being at substantially atmospheric pressure, theradial dimension of said radial gaps being such that the
liquid can be extracted and discharged through said through-
bores without any substantial drop in pressure in said pin-
barrel region and without clogging of said throughbores,
and
d) discharge network means, also at substantially
atmospheric pressure, in fluid flow communication with said
second end of each said throughbores.
The provision of said throughbores extending
axially in the pins and connected to a discharge network
enables the extracted liquid to be discharged at the site
at which it is produced, without a substantial pressure drop
being caused by the discharge apertures.
The pins prevent the material from rotating with
the screw, so that a high conveying output is achieved and
consequently a hlgh pressure is built up in the pin-barrel
region. Because of the high pressure, the water contained
in the cells of the solid components of the material can be
extracted. Accordingly, beet leaves, beet slices and sludge
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can be extracted, the liquid being released and easily
discharged through the discharge bores formed in the pins.
This is because there is a high drop in pressure of, for
example, from 300 bars which is the pressure in the press
barrel and l bar (atmospheric pressure) in the discharge
bores.
Since the spacing or gap of the tips of the pins
from the bottom of the screw thread is relatively small,
for example, preferably in a practical preferred arrange-
ment 0.3 mm, it is also-possible for minute solid particles,
which do not block the discharge bores, to be simultaneously
discharged. The tips of the pins are preferably adapted to
the rounded shape of the core of the screw.
In one preferred embodiment, the pins are located
between helical portions of the flights, the flights having
radially extending bores formed therein, the radial bores
being connected to an axial bore formed in the interior of
the screw.
Such a measure makes it possible for the extracted
llquid lying in the bottom of the screw thread to pass into
the discharge bores formed in the pins and for the extracted
liquid located adjacent the internal surface of the barrel
to be discharged over the flight ridges, through the radial
bores in the flights and into the axial bore in the screw.
Such an arrangement means that substantially all of the
extracted liquid is immediately collected and discharged
whilst no substantial drop in pressure occurs in the barrel
itself due to the discharge of the liquid.
Desirably, the press barrel has at least one
region provided with at least one internal groove, the pins
being located in the at least one grooved region. Such
internal grooves are, for preference, axial grooves but may
also be helical grooves corresponding to the pitch of the
flights or extending in a direction counter to the pitch of
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the flights. The gro~ves may be triangular, rectangular
or semi-circular in cross-section.
Preferably, a plurality of pins are combined to
form a pin plane, the individual pins in each plane being
disposed
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at equiangularly spaced intervals around the periphery of the
pre~s barrel, esch pin bein8 capable of being screwed into
the press barrel and the depth of insertion of the pins into
the barrel being adjustable.
Such an arrangement also makes it possible for the
conveyance of the material to be maintained between the
individual pin plane~, because the grooves in the barrel
prevent the material from rotating with the press s¢rew.
~ecause of this intensified conveying effect, a high preQsure
10 iB produced which i~ e~sential for effective extraction.
high enough pressure enableg the water contained in the oell~
of the solid components to be released and consequently permits
high d~y-sub6tanoe contents to be achieved in a sin~le
operation in a continuous manner. Such an arrangement also
ensures that the extrscted liquid is aischarged at the site
where it i~ extracted without any substantial drop in pressure
occurrin~ ln the barrel.
~ he combination of a plurality of pins, eaoh provided
with a discharge bore, to form one or more pin planes, make~
it possible for the extracted liquid to be extracted
peripherally at a plurality of location~. ~he ad~ustability
Or the pins with regard to their depth of insertion does, of
course, produce a change in the conveying output and hence
a change in the build-up of prea~ure. ~owever, it permits
the extraction device to be adapted to extract llquids from
mistures in which the solid components are of different sizes.
Preferably, the pin6 each have a tip portlon
capable of sliding on the base of the thread of the screw, the
tip portions being made of a material having dry-running
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propertle~. Thus, the tips msy be made of bronze. ~his ensures
a long, relatively wear-free useful life for the tip~ of the pin8.
Further desirably, emali-bore tubes may be in~d intD
the end region of discharge bores formed in the pins facing
the screw, the tubes being conically inwardly tapering in a
direction towards the screw. This makes it possible for the
inlet apertures of the bores to be of small diameter. Such
a measure counteracts the blocking of the bores in the pin bore6
and hence in the discharge system in communication therewith,
Further preferably, at least the portions of the pins
which extend into the interior of the press barrel are of
rectangular or polygonal cro6s-section. ~uch an arrangement
provides a shearing effect which cau6es the cutting-up of solid
particles as the particles are conveyed between the gaps $n the
flights and the pin members.
RIEF DESCRIPTION OF T~E DRAWINGS
Preferred embodiments of the present invention will be
further described, by way of example, with reference to the
accompanying drawings, in which:-
Fig. 1 i6 a diagrammatic longitudinal section through an
extraction device in accordance with thq present invention;
Fig. 2 i~ a cros6-sectional view taken along the line
II-II in Fig. l; and
Fig. 3 is a diagrammatic longitudinal section through
a slightly modified embodiment of the device.
DESCRIP~ION OF T~E PREFERRED EM~ODI~NTS
In the drawings, there i8 6hown a rotatable
extraction screw 1 which iB disposed in a pres6
barrel 2. The screw is rotated in the
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direction of arrow l9 by a drive unit (not shown). This
cause~ material to be extracted to be conveyed forwardly (from
right to left as seen in Fig. l) towards an outlet aper'ure 20.
Grooves 3 extending parallel to the longitudinal axis
of the screw l are formed in the interior surface of the barrel
2. These grooves 3 are preferably triangular in cross-section
but may also be rectangular or semi-circular in cross-section.
The grooves 3 are continuous, that is to say, they are provided
both in eed region 4 and in pin-barrel region 5 of the device.
In the pin-barrel region 5, pins 6 extend into the
interior of the barrel 2. The pins 6 extend radially towards
the longitudinal axis of the screw l and extend to the base of
the thread of the screw l. The pins 6 are associated with
gaps 7 formed in helically extending flights 8, the flights 8
defining the thread of the Rcrew l. The width of the gaps 7
corresponds to the diameter of the pins 6.
The pin~ 6 are screw-threadedly fitted into the press
barrel 2 and are retained by mean6 of nuts 9. The depth to
which ea¢h pin 6 is screwed into the pre6s barrel 2 i5
adjustable so that the distance between the tip Or the pin
and the core of the screw l can be varied.
The pins 6 are combined to form individual pin planes lO,
ll and 12. The pin plane ll is shown in cross-section in
~ig. 2. In 6uch embodiments four pins 6 are provided at
equiangularly spaced intervals around the periphery of the screw,
which pins have been combined to form the pin plane. It will,
however, be readily apparent that considerably more individual
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ping 6 may be disposed around the periphery of the wor~ and
combined into a pin plane. The number of pins employed is
dependent on the liquid, usually water, content of the material
to be extracted.
An axial discharge bore 13 is formed in each of the pin3 6,
the bores 13 being connected to a discharge network 14.
When the extraction device is not extracting material,
the tips of the pins do not touch the screw 1. If, however,
pressure builds up in chamber 18, that is to say, the interior
of the barrel 2, then the possibility of the end surfaces 15
of the pins 6 touching the worm cannot be excluded.
~he end or sliding surfaces 15 of the pins 6 facing the
core of the screw may therefore be made of a material which
has dry-running properties or may be made of bronze in order
to reduce wear phenomena.
Small bore tubes 16 may be inserted in the ends of the
discharge bores 13 located adjacent the core of the screw.
~hese tubes 16 taper conically inwards in a direction towards
the ¢ore of the screw 1. The conical design of the tubes 16
prevents blocking of the bores 13 because solid components can
only enter the bores 13 if they are smaller than the gap
between the sliding surface 15 of the pins and the core of the
screw 1.
A mixture of liquids and solids is introduced th~ugh
a funnel 17 into the chamber 18 defined between the individual
worm flights 8 and the internal surface of the barrel 2 and,
as previously mentioDed, is conveyed in the direction of the
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outlet aperture 20 by the rotational movement, in the
direction of arrow 19, of the worm 1.
In the feed region 4, the material is subjected to a
first compression, and liquid which is easily extractable from
the mixture flows into a collection vessel 22 through filter
apertures 21. Thereafter, the material is conveyed into the
pin-barrel region 5 where it is prevented from rotating with
the screw by the pins 6 which protrude into the press barrel
2. Material therefore tends to accumulate, for a short time,
upstream (in the direction of flow of the material) of the pins
6. The 2ressure in the screw thread therefore increases. Such
material in the thread will only progress, due to the pressure
of mixture components upstream thereof when the rotating screw
thread passeæ a free portion of the internal periphery of the
barrel 2, that is to say, a portion which is not obstructed by
pins 6.
Since the grooves 3, which extend parallel to the long-
itudinal axis of the screw, are disposed between the individual
pin planes 10, 11 and 12, the material to be extracted is also
prevented from rotating with the screw between such pin planes.
~his is because material is pressed into the grooves 3 and is
prevented from rotating with the screw 1. However, the
material iE subjected to a rolling movement. ~ecause of thiæ,
and due to the retardin~ effect of the pins 6 on the mixture,
a pres~ure builds up which cau~es the screw to produce a higher
throughput. ~he increase in the conveying output leads, of
necessity, to a considerable increase in pressure in the chamber
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_ g _
18 o~, for example, up to 500 bars, especially in the regions
between the pin planes 10, 11 and 12.
The greatest pressure on the material to be extracted
is the~efore exerted in the pin-barrel 5 whereby the water in
the cells of the solid components is released. The dry-sub-
stance content of the material can thus be increased to about
90% in a single continuous operation although this depends on
the material being proceæsed.
The outlet aperture 20 is sealable by means of pre~sure-
loaded cone 23 which causes the outlet aperture 20 to open
only when a specific, preselected, pressure has been reached.
~ecause of this provision, a further pressure increase is also
produced in the pin-barrel region 5.
The most essential pre-requisite for a high degree of
water extraction from a liquid-solid mixture is, however, the
provi~ion of the discharge bores 13 extending axially in the
pin~ 6, because this provides a means for the discharging liquid
which has been extracted in the region of the extraction device
it has been produced. In particular, the water contained in
the cells of the solid components is extracted aue to the very
high pressure and discharged from the device in substantially
the sa~e region.
It ie also highly desirable to discharge the extracted
liquid, from the site of extraction~ if this is possible,
whilst preventing the liquid from re-mixing with the solid
matter to any appreciable extent.
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~ y providing the discharge bores 13 in the pins 6,
it i~ pos~ible for the water or liquid contained in the cells
and extracted therefrom to be di~charged without any
substantial losa of pressure occurring in the pin-barrel
region 5. Conversely, the high build-up of pressure
- necessary for the extraction of the cell water or liquid
permits the attainment of high dry-substance contents.
As an example, beet leaves were inæerted into the
funnel 17 and passed continuously through the extraction device.
A dry ~ubstance content of 40% was achieved in a single
pas6age, which is an extremely high output.
Fig. 3 shows a slightly modified device, wherein the
pins 6 having discharge bores 13 are disposed between the
helical flight portionsg now referenced 24, ~owever, the
ridges of the flight portions 24 have radially inwardly
extending bores 25 formed therein, the bores 25 communicating
with an axial bore 26 formed in the interior of the core
of the screw 1.
The flight portions 24 in ~ig. 3 may also be provided
with a groove 27 extending along the ridge thereof, which
collects any liquid flowing over the flight 24 and conveys
it to the radial bores 25. The groove 27 therefore ensures
that any liquid flowing over the flight 24 is collected and
discharged.
The device shown in ~ig. 3 therefore has the advantage
that extracted liquid, which collects in the bottom of the
screw thread, can flow away through the discharge bores 13
formed in the pins 6, which pins extend to the bottom of the
screw thread. The extracted cell water, which should be
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located on the opposite aide of the internal surface
of the press barrel 2, ~ay flow away, via the worm
flight 24, into the ridge groove 27, thence into the
bore6 25 and the axial bore 26 in the screw 1.
Such an arrangement of the ~ins 6 therefore createa,
a plurality of different discharge channels for the
extracted liquid in the screw thread. ~ecause of the very high
drop in pressure, the liquid finds its way independently
between the screw thread and the discharge channels. The
drop in pressure also ensures that smaller solid components
are expelled from the various channels.
